Abstract:

Digital papillary adenocarcinoma (DPA) is a rare neoplasm that can exhibit local recurrence and distant metastasis. It is thus important to distinguish this entity from its benign mimickers. Here we present a case series with variable clinical presentation and morphology. Case 1 is that of a 45-year-old male with a 1.5-cm painful, wart-like, draining right thumb mass that had grown over two years despite eight attempts at cauterization. The lesion is in the deep dermis and consists of a solid architecture with papillary structures of atypical epithelioid cells with nucleoli in the hyalinized stroma. Necrosis and many mitoses are seen. Case 2 is from a 36-year-old male who presented with a small, painless nodule in the finger, which was discovered after a splinter injury. The lesion is composed of small nests and cystic structures lined by bland-looking cells. Scant necrosis, scattered mitoses, and abundant calcifications are present. Case 3 is a 36-year-old female with a very slow-growing nodule in her right dorsal finger that appeared shortly after birth. The nodule had gotten slightly bigger and become tender. Case 4 is an excisional biopsy from a 60-year-old male with a small nodule in the left mid-dorsal hand, diagnosed clinically as an atypical nevus. The lesions in cases 3 and 4 are both small, well-defined, confined in the dermis, and have similar morphology. They are composed of glandular structures lined by bland-looking cuboidal epithelium with luminal papillary infoldings within a fibrotic stroma and rare mitoses but no necrosis. Case 1 exhibits a more aggressive clinical course and high-grade morphology and is negative for BRAF. In contrast, the other three cases feature a more indolent course and bland morphology and are positive for BRAF. These findings suggest that indolent forms of DPA with low-grade microscopic findings are associated with BRAF mutations.

Financial Disclosure:
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