A basaloid follicular hamartoma is a cutaneous condition characterized as distinctive benign adnexal tumor that has several described variants.

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.

An acanthoma is a skin neoplasm composed of squamous or epidermal cells. It is located in the prickle cell layer.

Types of acanthoma include pilar sheath acanthoma, a benign follicular tumor usually of the upper lip; clear cell acanthoma, a benign tumor found most frequently on the legs; and Degos acanthoma, often confused with but unrelated to Degos disease.

Hidradenocarcinoma (also known as malignant hidradenoma, malignant acrospiroma, clear cell eccrine carcinoma, or primary mucoepidermoid cutaneous carcinoma) is a malignant adnexal tumor of the sweat gland. It is the malignant variant of the benign hidradenoma. It may develop de novo or in association with an existent hidradenoma.

This type of tumor typically develops in older individuals (after age 40).

Hidradenoma (also known as acrospiroma, from "akral ""peripheral"" + spiroma ""epithelial tumor of sweat gland") refers to a benign adnexal tumor of the apical sweat gland. Another name for Hidradenoma is Cystadenoma and Hydrocystadenomas. These are 1–3 cm translucent blue cystic nodules.It usually presents as a single, small skin-colored lesion, and is considered distinct from the closely related poroma. Hidradenomas are often sub-classified based on subtle histologic differences, for example:

- clear-cell hidradenoma or acrospiroma

- nodular hidradenoma or acrospiroma

- solid-cystic hidradenoma

Discussion of sweat gland tumors can be difficult and confusing due to the complex classification and redundant terminology used to describe the same tumors. For example, acrospiroma and hidradenoma are synonymous, and sometimes the term "acrospiroma" is used to generally describe benign sweat gland tumors. In addition, a single lesion may contain a mixture of cell-types. There has also been a change in understanding about how tumors that were previously believed to strictly derive from specific sweat gland types may, in fact, derive from both eccrine "or" apocrine glands.

Hidradenomas are by definition benign, with malignant transformation very rare. When tumors show malignant characteristics, they are known as hidradenocarcinoma. Surgical excision is usually curative and local recurrences are rare, although malignant tumors may metastasize.

In dermatologic pathology, a dermal cylindroma, also dermal eccrine cylindroma or Cutaneous Cylindroma) and (less specifically) cylindroma, is a benign adnexal tumor, which occurs on the scalp and forehead.when multiple Cylindroma-Show Hat like configration.

Multiple cylindromas may grow together in a "hat-like" configuration, sometimes referred to as a turban tumor. Cylindromas are uncommon dysplasias of skin appendages.

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.

Adnexal and skin appendage neoplasms is a group of tumors which develop in the adnexal skin structures such as the sweat and sebaceous glands. An example is the hidrocystoma.

This type of carcinoma is commonly managed by local resection, cryotherapy, topical chemotherapy, and radiotherapy. Multimodal therapy has been shown to improve both visual prognosis and survival.

Mohs micrographic surgery has become the treatment of choice for this form of cancer. When used as the primary treatment modality for sebaceous carcinoma of the eyelid, Mohs surgery is associated with significantly lower local and distant recurrence rates.

Hamartomas, while generally benign, can cause problems due to their location. For example, when located on the skin, especially on the face or neck, they can be very disfiguring. Cases have been reported of hamartomas the size of a small orange. They may obstruct practically any organ in the body, such as the colon, eye, etc. They are particularly likely to cause major health issues when located in the hypothalamus, kidneys, lips, or spleen. They can be removed surgically if necessary, and are not likely to recur. Prognosis will depend upon the location and size of the lesion, as well as the overall health of the patient.

Microcystic adnexal carcinoma (also known as sclerosing sweat duct carcinoma) is a cutaneous condition characterized by a slow-growing plaque or nodule.

Warty dyskeratoma must be differentiated from vulvar dysplasia, Bowenoid papulosis, squamous carcinoma, condyloma, and other viral-induced squamous lesions.

Extramammary Paget's disease is usually seen in isolation and is associated with an underlying invasive malignancy about 12% of the time. It is associated with an underlying adnexal malignancy about 24% of the time. Paget's disease of the breast is almost always associated with an underlying invasive malignancy, i.e. breast cancer (e.g. mammary ductal carcinoma).

Carcinoma "in situ" is, by definition, a localized phenomenon, with no potential for metastasis unless it progresses into cancer. Therefore, its removal eliminates the risk of subsequent progression into a life-threatening condition.

Some forms of CIS (e.g., colon polyps and polypoid tumours of the bladder) can be removed using an endoscope, without conventional surgical resection. Dysplasia of the uterine cervix is removed by excision (cutting it out) or by burning with a laser. Bowen's disease of the skin is removed by excision. Other forms require major surgery, the best known being intraductal carcinoma of the breast (also treated with radiotherapy). One of the most dangerous forms of CIS is the "pneumonic form" of BAC of the lung, which can require extensive surgical removal of large parts of the lung. When too large, it often cannot be completely removed, with eventual disease progression and death of the patient.

Trichoepitheliomas consisted of nests of basaloid cells. They lack the myxoid stroma and artefactual clefting seen in basal cell carcinoma. Mitoses are uncommon when compared to basal cell carcinoma.

Warty dyskeratoma, also known as an Isolated dyskeratosis follicularis, is a benign epidermal proliferation with distinctive histologic findings that may mimic invasive squamous cell carcinoma and commonly manifests as an umbilicated (Having a central mark or depression resembling a navel) lesion with a keratotic plug, WD have some histopathologic similarities to viral warts but it's not caused by HPV and the majority of these lesions display overall histopathologic features consistent with a follicular adnexal neoplasm. usually limited to the head, neck, scalp or face and vulva. Lesions are generally and sporadic and may be associated with a follicular unit. Oral involvement, particularly the hard palate, and genital involvement have been reported. it can also be thought of as one of the manifestations of focal acantholytic dyskeratosis, an epidermal reaction pattern that can be seen in several disorders, including Darier's disease and Grover's disease. But the main Difference between Darier disease and Warty dyskeratoma, is that Darier disease inherited dermatosis (autosomal dominant) consisting of multiple keratotic papules on the face, trunk, and extremities, while WD occurs as an isolated, noninherited, single keratotic nodule mainly confined to the head and neck as mentioned earlier.

Metastatic carcinoma is able to grow at sites distant from the primary site of origin; thus, dissemination to the skin may occur with any malignant neoplasm, and these infiltrates may result from direct invasion of the skin from underlying tumors, may extend by lymphatic or hematogenous spread, or may be introduced by therapeutic procedures.

The most common malignancy found in bone is metastatic carcinoma.

Dermal cylindromas are:

- dermal lesions consisting of nests of cells that are surrounded by hyaline (i.e. glassy, eosinophilic, acellular) material and have:

- hyperchromatic nuclei that may palisade (columnar nuclei arranged around the periphery of the cells nests - with their short axis tangential to the nest periphery), and

- cells with lighter staining ovoid nuclei at their centre.

They lack of a significant number of lymphocytes; this differentiates them from spiradenomas.

Acrospiroma (also known as hidradenoma) is a cutaneous condition, primarily occurring in adult women, that is a form of benign adnexal neoplasm closely related to poroma.

Although not specific to one mode of management, lesion size, patient sex, or follow-up, the recurrence rate for chondroblastoma is relatively high, and has been shown in select studies to be dependent upon the anatomical location, method of treatment, and biological aggressiveness of the initial lesion. The rate of recurrence is highly variable, ranging between 5% and 40%, as study results are generally inconclusive. However, local recurrence for long bone lesions is around 10%, with chondroblastoma in flat bones having higher recurrence and more complications. Recurrences are more common in cases involving an open epiphyseal plate where they can be attributed to inadequate curettage to avoid damage. Lesions of the proximal femur are particularly problematic because of difficulties accessing the femoral head for complete excision. Chondroblastoma may recur in the soft tissue surrounding the initial lesion, especially in the case of incomplete curettage. Recurrences have been shown to occur between 5 months and 7 years after initial treatment and are generally treated with repeat curettage and excision of affected soft-tissue. No histological differences have been seen between recurrent and non-recurrent chondroblastomas.

Rarely, more aggressive chondroblastomas can metastasize. The most common location for metastases is the lung, with some cases also involving secondary bone sites, soft tissue, skin, or the liver. The prevalence of metastatic chondroblastoma, however, is quite low and is believed to be less than 1%. There is no relationship established between metastasis and previous surgery, non-surgical treatment, anatomical location, or patient age. Survival of patients with metastatic lesions is better when the metastases are surgically resectable, as chemotherapy has been shown to have little to no benefit. Prognosis is bleak for patients with malignant chondroblastomas that are resistant to surgery, radiation, and chemotherapy. However, patients with resectable metastases have survived for several years following diagnosis.

While recurrence is the most common complication of chondroblastoma other issues include post-surgery infection, degenerative joint disease, pathological fractures, failure of bone grafts, pre-mature epiphyseal closure, functional impairment, and malignant transformation. Complications are less common in patients presenting with chondroblastoma in accessible areas. Overall, patients with more classical chondroblastoma (appearing in long bones, typical presentation) have better prognoses than patients with atypical chondroblastoma (flat bones, skull, etc.).

Considered part of the PTEN hamartoma tumor syndrome (PHTS), which also includes Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like syndrome, Cowden syndrome is a serious genetic disorder characterized by multiple hamartomas. Usually skin hamartomas exist, and commonly (in about 66% of cases) hamartoma of the thyroid gland exists. Additional growths can form in many parts of the body, especially in bones, CNS, the eyes, the genitourinary tract, the GI tract, and mucosa. The hamartomas themselves may cause symptoms or even death, but morbidity is more often associated with increased occurrence of malignancies, usually in the breast or thyroid.

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare subtype of renal cell carcinoma (RCC), that is included in the 2004 WHO classification of RCC. MTSCC is a rare neoplasm and is considered as a low-grade entity. It may be a variant of papillary RCC. This tumor occurs throughout life (age range 17–82 years) and is more frequent in females.

Carcinoma "in situ (CIS), also known as in situ" neoplasm, is a group of abnormal cells. While they are a form of neoplasm there is disagreement over whether CIS should be classified as cancer. This controversy also depends on the exact CIS in question (i.e. cervical, skin, breast). Some authors do not classify them as cancer, however, recognizing that they can potentially become cancer. Others classify certain types as a non-invasive form of cancer. The term "pre-cancer" has also been used.

These abnormal cells grow in their normal place, thus ""in situ"" (from Latin for "in its place"). For example, carcinoma "in situ" of the skin, also called Bowen's disease, is the accumulation of dysplastic epidermal cells within the epidermis only, that has failed to penetrate into the deeper dermis. For this reason, CIS will usually not form a tumor. Rather, the lesion is flat (in the skin, cervix, etc.) or follows the existing architecture of the organ (in the breast, lung, etc.). Exceptions include CIS of the colon (polyps), the bladder (preinvasive papillary cancer), or the breast (ductal carcinoma "in situ" or lobular carcinoma "in situ").

Many forms of CIS have a high probability of progression into cancer, and therefore removal may be recommended; however, progression of CIS is known to be highly variable and not all CIS becomes invasive cancer.

In the TNM classification, carcinoma "in situ" is reported as TisN0M0 (stage 0).

Paget's disease of the vulva, a rare disease, may be a primary lesion or associated with adenocarcinoma originating from local organs such as the Bartholin gland, the urethra, or the rectum and thus be secondary. Patients tend to be postmenopausal.

Paget's disease of the penis may also be primary or secondary, and is even rarer than genital Paget’s disease in women. At least one case has been misdiagnosed as Bowen's disease. Isolated Paget's disease of the penis is extremely rare.

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.