Bowen's disease typically presents as a gradually enlarging, well-demarcated red colored plaque with an irregular border and surface crusting or scaling. Bowen's disease may occur at any age in adults, but is rare before the age of 30 years; most patients are aged over 60. Any site may be affected, although involvement of palms or soles is uncommon. Bowen's disease occurs predominantly in women (70–85% of cases). About 60–85% of patients have lesions on the lower leg, usually in previously or presently sun-exposed areas of skin.

This is a persistent, progressive, unelevated, red, scaly or crusted plaque which is due to an intraepidermal carcinoma and is potentially malignant. The lesions may occur anywhere on the skin surface, including on mucosal surfaces. Freezing, cauterization, or diathermy coagulation is often effective treatment. Pathomorphologic study of tissue sampling revealed: polymorphism of spiny epithelial cells has progressed into atypism; increased mitosis; giant and multinucleate cells; acanthosis; hyperkeratosis and parakeratosis; basal membrane and basal layer are retained.

MCC usually presents as a firm, painless, nodule (up to 2 cm diameter) or mass (>2 cm diameter). These flesh-colored, red, or blue tumors typically vary in size from 0.5 cm (less than one-quarter of an inch) to more than 5 cm (2 inches) in diameter, and usually enlarge rapidly. Although MCC's may arise almost anywhere on the body, about half originate on sun-exposed areas of the head and neck, one-third on the legs, and about one-sixth on the arms. In about 12% of cases, no obvious anatomical site of origin ("primary site") can be identified.

Merkel-cell cancers tend to invade locally, infiltrating the underlying subcutaneous fat, fascia, and muscle, and typically metastasize early in their natural history, most often to the regional lymph nodes. MCCs also spread aggressively through the blood vessels, particularly to liver, lung, brain, and bone.

Patients typically present with a non-productive cough and weight loss.

Primary squamous cell thyroid carcinoma shows an aggressive biological phenotype resulting in poor prognosis for patients.

Most bladder cancer is transitional cell, but bladder cancer associated with Schistosomiasis is often squamous cell carcinoma.

Clear cell papillary renal cell carcinoma, abbreviated CCPRCC and also known as clear cell tubulopapillary renal cell carcinoma, is a rare subtype of renal cell carcinoma (RCC) that has microscopic morphologic features of papillary renal cell carcinoma and clear cell renal cell carcinoma, yet is pathologically distinct based on molecular changes and immunohistochemistry.

A Clear-cell carcinoma is a carcinoma (i.e. not a sarcoma) showing clear cells.

"A rare type of tumor, usually of the female genital tract, in which the insides of the cells look clear when viewed under a microscope. Also called clear cell adenocarcinoma and mesonephroma."

Examples :

- Clear cell renal cell carcinoma ~ clear cell kidney cancer

- Uterine clear-cell carcinoma ~ clear cell endometrial cancer

- Clear-cell ovarian carcinoma

Individuals with a basal-cell carcinoma typically present with a shiny, pearly skin nodule. However, superficial basal-cell cancer can present as a red patch similar to eczema. Infiltrative or morpheaform basal-cell cancers can present as a skin thickening or scar tissue – making diagnosis difficult without using tactile sensation and a skin biopsy. It is often difficult to visually distinguish basal-cell cancer from acne scar, actinic elastosis, and recent cryodestruction inflammation.

Lung cancer is a large and exceptionally heterogeneous family of malignancies. Over 50 different histological variants are explicitly recognized within the 2004 revision of the World Health Organization (WHO) typing system ("WHO-2004"), currently the most widely used lung cancer classification scheme. Many of these entities are rare, recently described, and poorly understood. However, since different forms of malignant tumors generally exhibit diverse genetic, biological, and clinical properties — including response to treatment — accurate classification of lung cancer cases are critical to assuring that patients with lung cancer receive optimum management.

Under WHO-2004, lung carcinomas are divided into 8 major taxa:

- Squamous cell carcinoma

- Small cell carcinoma

- Adenocarcinoma

- Large cell carcinoma

- Adenosquamous carcinoma

- Sarcomatoid carcinoma

- Carcinoid tumor

- Salivary gland-like carcinoma

Salivary gland–like carcinomas of the lung generally refers a class of rare cancers that arise from the uncontrolled cell division (mitosis) of mutated cancer stem cells in lung tissue. They take their name partly from the appearance of their abnormal cells, whose structure and features closely resemble those of cancers that form in the major salivary glands (parotid glands, submandibular glands and sublingual glands) of the head and neck. Carcinoma is a term for malignant neoplasms derived from cells of epithelial lineage, and/or that exhibit cytological or tissue architectural features characteristically found in epithelial cells.

This class of primary lung cancers contains several histological variants, including mucoepidermoid carcinoma of the lung, adenoid cystic carcinoma of the lung, epithelial-myoepithelial carcinoma of the lung, and other (even more rare) variants. .

Bowen's disease, also known as squamous cell carcinoma" in situ" is a neoplastic skin disease. It can be considered as an early stage or intraepidermal form of squamous cell carcinoma. It was named after John T. Bowen.

Erythroplasia of Queyrat is a particular type of Bowen's disease that can arise on the glans or prepuce in males, and, on the vulva in females, and may be induced by human papilloma virus. It is reported to occur in the corneoscleral limbus.

The histopathologic classification includes:

- "Nodular basal cell carcinoma" (also known as "classic basal-cell carcinoma") most commonly occurs on the sun-exposed areas of the head and neck.

- "Cystic basal cell carcinoma" is morphologically characterized by dome-shaped, blue-gray cystic nodules.

- "Cicatricial basal cell carcinoma" (also known as "morpheaform basal cell carcinoma," and "morphoeic basal cell carcinoma") is an aggressive variant with a distinct clinical and histologic appearance.

- "Infiltrative basal cell carcinoma" is an aggressive type characterized by deep infiltration.

- "Micronodular basal cell carcinoma" is characterized by a micronodular growth pattern.

- "Superficial basal cell carcinoma" (also known as "superficial multicentric basal-cell carcinoma") occurs most commonly on the trunk and appears as an erythematous patch.

- "Pigmented basal cell carcinoma" exhibits increased melanization. About 80% of all basal-cell carcinoma in Chinese are pigmented while this subtype is uncommon in white people.

- "Rodent ulcer" (also known as a "Jacob's ulcer") is a large skin lesion of nodular basal-cell carcinoma with central necrosis. Almost all cancers can metastasize except glioma (maligancy of the central nervous system) and the rodent ulcer.

- "Fibroepithelioma of Pinkus" most commonly occurs on the lower back.

- "Polypoid basal cell carcinoma" is characterized by exophytic nodules (polyp-like structures) on the head and neck.

- "Pore-like basal cell carcinoma" resembles an enlarged pore or stellate pit.

- "Aberrant basal cell carcinoma" is characterized by the formation of basal-cell carcinoma in the absence of any apparent carcinogenic factor, occurring in odd sites such as the scrotum, vulva, perineum, nipple, and axilla.

See also:

- Nevoid basal-cell carcinoma syndrome

Basophilic, bland cells similar to acinar cells. Growth pattern: solid - acinar cells, microcytic - small systic spaces mucinous or eosinophilic, papillary-cystic - large cystic lined by epithelium, follicular - similar to thyroid tissue.

These tumors which resemble serous acinar cells vary in their behavior from locally aggressive to blatantly malignant.

It can also appear in the breast. The pancreatic form of acinic cell carcinoma is a rare subtype of exocrine pancreatic cancer. Exocrine pancreatic cancers are the most common form of pancreatic cancer when compared to endocrine pancreatic cancer.

Acinic cell carcinomas arise most frequently in the parotid gland. Other sites of primary tumors have included the submandibular gland and other major and minor salivary glands. There have been rare cases of primary tumors involving the parapharyngeal space and the sublingual gland.

Acinic cell carcinoma appears in all age groups, but presents at a younger median age (approx. 52 years) than most other salivary gland cancers. Occurrences in children are quite common.

Sebaceous carcinoma is an uncommon and aggressive malignant cutaneous tumor. Most are typically about 10 mm in size at presentation. This neoplasm is thought to arise from sebaceous glands in the skin and, therefore, may originate anywhere in the body where these glands are found. Because the periocular region is rich in this type of gland, this region is a common site of origin. The cause of these lesions are, in the vast majority of cases, unknown. Occasional cases may be associated with Muir-Torre syndrome.

This type of cancer usually has a poor prognosis because of a high rate of metastasis.

Clear-cell adenocarcinoma is a type of adenocarcinoma that shows clear cells.

Types include:

- Clear-cell adenocarcinoma of the vagina

- Clear-cell ovarian carcinoma

- Uterine clear-cell carcinoma

- Clear-cell adenocarcinoma of the lung (which is a type of Clear-cell carcinoma of the lung)

See also:

- Clear-cell squamous cell carcinoma of the lung

Large-cell carcinoma (LCC) is a heterogeneous group of undifferentiated malignant neoplasms that lack the cytologic and architectural features of small cell carcinoma and glandular or squamous differentiation. LCC is categorized as a type of NSCLC (Non-Small Cell Carcinoma) which originates from epithelial cells of the lung.

Often, this disease evolves from a precursor lesion, usually a dysplastic nevus. Otherwise it arises in previously normal skin. A prolonged radial growth phase, where the lesion remains thin, may eventually be followed by a vertical growth phase where the lesion becomes thick and nodular. As the risk of spread varies with the thickness, early SSM is more frequently cured than late nodular melanoma.

The microscopic hallmarks are:

- Large melanocytic cells with nest formation along the dermo-epidermal junction.

- Invasion of the upper epidermis in a pagetoid fashion (discohesive single cell growth).

- The pattern of rete ridges is often effaced.

- Invasion of the dermis by atypical, pleomorphic melanocytes

- Absence of the 'maturation' typical of naevus cells

- Mitoses

Adenosquamous lung carcinoma (AdSqLC) is a biphasic malignant tumor arising from lung tissue that is composed of at least 10% by volume each of squamous cell carcinoma (SqCC) and adenocarcinoma (AdC) cells.

Merkel-cell carcinoma (MCC) is a rare and highly aggressive skin cancer, which, in most cases, is caused by the Merkel cell polyomavirus (MCV) discovered by scientists at the University of Pittsburgh in 2008. It is also known as cutaneous APUDoma, primary neuroendocrine carcinoma of the skin, primary small cell carcinoma of the skin, and trabecular carcinoma of the skin.

Approximately 80% of Merkel-cell carcinomas are caused by MCV. The virus is clonally integrated into the cancerous Merkel cells. In addition, the virus has a particular mutation only when found in cancer cells, but not when it is detected in healthy skin cells. Direct evidence for this oncogenetic mechanism comes from research showing that inhibition of production of MCV proteins causes MCV-infected Merkel carcinoma cells to die but has no effect on malignant Merkel cells that are not infected with this virus. MCV-uninfected tumors, which account for approximately 20% of Merkel-cell carcinomas, appear to have a separate and as-yet unknown cause. These tumors tend to have extremely high genome mutation rates, due to ultraviolet light exposure, whereas MCV-infected Merkel cell carcinomas have low rates of genome mutation. No other cancers have been confirmed so far to be caused by this virus. Because of the viral origin for this cancer, immunotherapies are a promising avenue for research to treat virus-positive Merkel-cell carcinoma.

This cancer is considered to be a form of neuroendocrine tumor. While patients with a small tumor (less than 2 cm) that has not yet metastasized to regional lymph nodes have an expected 5-year survival rate of more than 80 percent, once a lesion has metastasized regionally, the rate drops to about 50 percent. Up to half of patients that have been seemingly treated successfully (i.e. that initially appear cancer-free) subsequently suffer a recurrence of their disease. Recent reviews cite an overall 5-year survival rate of about 60% for all MCC combined.

Merkel-cell carcinoma occurs most often on the sun-exposed face, head, and neck.

SCC of the skin begins as a small nodule and as it enlarges the center becomes necrotic and sloughs and the nodule turns into an ulcer.

- The lesion caused by SCC is often asymptomatic

- Ulcer or reddish skin plaque that is slow growing

- Intermittent bleeding from the tumor, especially on the lip

- The clinical appearance is highly variable

- Usually the tumor presents as an ulcerated lesion with hard, raised edges

- The tumor may be in the form of a hard plaque or a papule, often with an opalescent quality, with tiny blood vessels

- The tumor can lie below the level of the surrounding skin, and eventually ulcerates and invades the underlying tissue

- The tumor commonly presents on sun-exposed areas (e.g. back of the hand, scalp, lip, and superior surface of pinna)

- On the lip, the tumor forms a small ulcer, which fails to heal and bleeds intermittently

- Evidence of chronic skin photodamage, such as multiple actinic keratoses (solar keratoses)

- The tumor grows relatively slowly

Lung cancers have been historically classified using two major paradigms. Histological classification systems group lung cancers according to the appearance of the cells and surrounding tissues when they are viewed under a microscope. Clinical classification systems divide lung cancers into groups based on medical criteria, particularly their response to different treatment regimens.

Before the mid-1900s, lung cancer was considered to be a single disease entity, with all forms treated similarly. In the 1960s, small cell lung carcinoma (SCLC) was recognized as a unique form of lung cancer, based both on its appearance (histology) and its clinical properties, including much greater susceptibility to chemotherapy and radiation, more rapid growth rate, and its propensity to metastasize widely early on in its course. Since then, most oncologists have based patient treatment decisions on a dichotomous division of lung cancers into SCLC and non-small cell lung carcinomas (NSCLC), with the former being treated primarily with chemoradiation, and the latter with surgery.

An explosion of new knowledge, accumulated mainly over the last 20 years, has proved that lung cancers should be considered an extremely heterogeneous family of neoplasms with widely varying genetic, biological, and clinical characteristics, particularly their responsiveness to the large number of newer treatment protocols. Well over 50 different histological variants are now recognized under the 2004 revision of the World Health Organization ("WHO-2004") typing system, currently the most widely used lung cancer classification scheme. Recent studies have shown beyond doubt that the old clinical classification paradigm of "SCLC vs. NSCLC" is now obsolete, and that correct "subclassification" of lung cancer cases is necessary to assure that lung cancer patients receive optimum management.

Approximately 98% of lung cancers are carcinoma, which are tumors composed of cells with epithelial characteristics. LCLC's are one of 8 major groups of lung carcinomas recognized in WHO-2004:

- Squamous cell carcinoma

- Small cell carcinoma

- Adenocarcinoma

- Large cell carcinoma

- Adenosquamous carcinoma

- Sarcomatoid carcinoma

- Carcinoid tumor

- Salivary gland-like carcinoma

Trichoepithelioma is a neoplasm of the adnexa of the skin. Its appearance is similar to basal cell carcinoma.

One form has been mapped to chromosome 9p21.

Keratoacanthomas (molluscum sebaceum) may be divided into the following types:

- "Giant keratoacanthomas" are a variant of keratoacanthoma, which may reach dimensions of several centimeters.

- "Keratoacanthoma centrifugum marginatum" is a cutaneous condition, a variant of keratoacanthomas, which is characterized by multiple tumors growing in a localized area.

- "Multiple keratoacanthomas" (also known as "Ferguson–Smith syndrome," "Ferguson-Smith type of multiple self-healing keratoacanthomas,") is a cutaneous condition, a variant of keratoacanthomas, which is characterized by the appearance of multiple, sometimes hundreds of keratoacanthomas.

- A "solitary keratoacanthoma" (also known as "Subungual keratoacanthoma") is a benign, but rapidly growing, locally aggressive tumor which sometimes occur in the nail apparatus.

- "Generalized eruptive keratoacanthoma" (also known as "Generalized eruptive keratoacanthoma of Grzybowski") is a cutaneous condition, a variant of keratoacanthomas, characterized by hundreds to thousands of tiny follicular keratotic papules over the entire body. Treatments are not successful for many patients with Generalized eruptive keratoacanthoma. Use of emollients and anti-itch medications can ease some symptoms. Improvement or complete resolutions of the condition has occurred with the application of the following medications: Acitretin, Isotretinoin, Fluorouracil, Methotrexate, Cyclophosphamide.

Well-differentiated and moderately differentiated sebaceous carcinoma tend to exhibit vacuolization within the cytoplasm of the tumor cells. Histology may mimic basal cell carcinoma.