Eccrine Carcinoma, Arising in Hidradenoma (Hidradenocarcinoma)

    A 78 year-old woman presented with a 3 X 2 cm dermal nodule on the scalp. The clinical differential diagnosis was cylindroma plexiform neurofibroma vs angiofibroma. A punch biopsy in the middle of the lesion was performed.

     

    Follow up:

    The following diagnosis was rendered: "Epithelial tumor with eccrine differentiation in deep dermis, extending to specimen margins, see note. Note: The lesion is positive for keratin and negative for SMA consistent with an appendageal tumor, most suggestive of nodular hidradenoma. No necrosis, significant cytologic atypia or mitoses are seen, however the lateral  circumscription, infiltrative nature or potential behavior cannot be determined on this incisional biopsy.” A complete excision was recommended which was performed.

     

    Discussion:

    Cutaneous sweat gland tumors can present diagnostic challenges because they are uncommon and can have a variety of  histologic appearances that define different subtypes (which have many different names). The most important decision is benign vs. malignant.

     

    Benign

    Well-circumscribed, lobular growth

    Two cell layers to ducts

    Clear cell change, squamoid areas, papillary apocrine features

    Fibrous stroma, thick capsule

    Small dark nuclei, minimal pleomorphism

    Rare mitoses, no necrosis

     

    Malignant

    Infiltrative edges

    Tumor invades capsule

    Mucin pools

    Large, pleomorphic nuclei

    Mitotic activity

    Necrosis

    Perineural invasion

    Recurrence after incomplete excision

    Conference: