Pathology of the Vulva and Vagina by Laurence Brown

Author:Laurence Brown
Language: eng
Format: epub
Publisher: Springer London, London

Differential Diagnosis

As discussed earlier, genital melanomas must be separated from genital melanosis and benign melanocytic nevi, in particular dysplastic and atypical genital nevi. Non-melanocytic tumors also enter the differential diagnosis. Most relevant is distinction from Paget’s disease and poorly differentiated squamous cell carcinoma as there may be significant morphological overlap.

Paget’s disease is characterized by an intraepidermal proliferation of epithelial cells. These cells are present as single cells or in small groups or nests. They are present at the level of the epidermal basal cell layer and show florid upward, so-called pagetoid spread. The morphological appearances are highly reminiscent of those seen in in situ melanoma. Occasionally, an invasive dermal component may also be present. Helpful histological clues to the correct diagnosis of Paget’s disease include the presence of cytoplasmic mucin and glandular differentiation. The diagnosis can easily be confirmed by histochemistry with PAS/PAS-diastase-positive cells and immunohistochemistry with positivity for cytokeratins and CEA but negative staining for markers of melanocytic differentiation.

Helpful features in the distinction from poorly differentiated squamous cell carcinoma include the identification of better differentiated areas with evidence of keratinization and visualization of intercellular bridges in squamous cell carcinoma and the presence of an in situ component in melanoma. In difficult cases, the problem can usually be solved using immunohistochemistry for melanocytic markers such as S100 protein and Melan A in addition to cytokeratins.

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