Tubular apocrine adenoma clinically and dermoscopically mimicking basal cell carcinoma
Authors: Takamasa Ito, Toshifumi Nomura, Yasuyuki Fujita, Riichiro Abe, Hiroshi Shimizu
Journal: Journal of the American Academy of Dermatology (2014)

To the Editor: Tubular apocrine adenoma (TAA) is a rare benign sweat gland tumor, typically presenting as a well-defined, red to brownish nodule on the scalp. TAA is histologically characterized by a well-circumscribed intradermal mass comprising tubular structures lined with two rows of epithelial cells.1Landry M. Winkelmann R.K. An unusual tubular apocrine adenoma.Arch Dermatol. 1972; 105: 869-879Crossref PubMed Scopus (80) Google Scholar, 2Mitsuishi T. Kawana S. Tubular apocrine adenoma of the nose.Eur J Dermatol. 2011; 21: 132PubMed Google Scholar The cells forming the tubular structures show apocrine differentiation with decapitation secretion.1Landry M. Winkelmann R.K. An unusual tubular apocrine adenoma.Arch Dermatol. 1972; 105: 869-879Crossref PubMed Scopus (80) Google Scholar, 2Mitsuishi T. Kawana S. Tubular apocrine adenoma of the nose.Eur J Dermatol. 2011; 21: 132PubMed Google Scholar Although TAA has been histologically well characterized, the dermoscopic features of TAA have not been reported. Here, we present a case of TAA with dermoscopic findings that are indistinguishable from those of basal cell carcinoma (BCC).A 63-year-old man presented with a 2-month history of a small black papule progressively growing on his face. On physical examination, a 3-mm-diameter well-circumscribed black papule with a pearly border was seen on his left cheek (Fig 1, A). Dermoscopic examination revealed telangiectasias and round or oval bluish gray areas that we considered to be short fine telangiectasias (SFTs) and large blue-gray ovoid nests, respectively (Fig 1, B). From the clinical and dermoscopic findings, BCC was initially suspected. Histology showed a number of irregularly shaped tubular structures in the dermis (Fig 2). Telangiectasias were also evident in the upper dermis. The tubular structures contained 2 or more layers of epithelial cells filled with abundant red blood cells (RBCs) and eosinophilic fluid. The luminal layer of the tubular structures was composed of columnar cells, and the outer layer consisted of cuboidal cells. The luminal cells showed active decapitation secretion. Immunohistochemically, positive staining for gross cystic disease fluid protein-15 was observed in the columnar and cuboidal cells and the luminal fluids. The tumor cells showed no significant nuclear atypia or mitotic figures. Neither epidermal invagination nor infiltration of plasma cells was seen. These findings collectively supported a diagnosis of TAA.Fig 2Tubular apocrine adenoma. Histologic findings of the nodule. The histology of the nodule shows an intradermal nodule composed of variable sized tubular structures without connection to the follicular infundibulum. Note that numerous red blood cells are observed in the tubular structures. (Hematoxylin-eosin stain; original magnification ×12.5.)View Large Image Figure ViewerDownload Hi-res image Download (PPT)Clinically, a black lesion with a pearly border developed on our patient's face and showed SFTs and large blue-gray ovoid nests under dermoscopy. Therefore, we initially diagnosed the lesion as BCC. However, subsequent histologic examinations led to a diagnosis of TAA. To our knowledge, to date, no case of TAA showing clinical or dermoscopic resemblance to BCC has been reported. Notably, both SFTs and well-established large blue-gray ovoid nests were observed in the same lesion, although their coexistence is rare in BCC.3Altamura D. Menzies S.W. Argenziano G. Zalaudek I. Soyer H.P. Sera F. et al.Dermoscopy of basal cell carcinoma: morphologic variability of global and local features and accuracy of diagnosis.J Am Acad Dermatol. 2010; 62: 67-75Abstract Full Text Full Text PDF PubMed Scopus (253) Google Scholar Moreover, large blue-gray ovoid nests were arranged in a floriform pattern. The coexistence of SFTs and mature large blue-gray ovoid nests and/or the peculiar arrangement of the ovoid nests might be specific dermoscopic features of TAA. In addition to the typical histologic features of TAA, numerous RBCs in the tubular structures were uniquely observed in this case (Fig 2), presumably giving an atypical color to the lesion. Thus, we speculate that the large blue-gray ovoid nests histologically correspond to the tubular structures filled with numerous RBCs. SFTs also correspond to histologic telangiectasias observed in the upper dermis.In summary, our case suggests that TAA could mimic pigmented BCC clinically and dermoscopically, especially when SFTs and large blue-gray ovoid nests in a floriform pattern are seen dermoscopically. To the Editor: Tubular apocrine adenoma (TAA) is a rare benign sweat gland tumor, typically presenting as a well-defined, red to brownish nodule on the scalp. TAA is histologically characterized by a well-circumscribed intradermal mass comprising tubular structures lined with two rows of epithelial cells.1Landry M. Winkelmann R.K. An unusual tubular apocrine adenoma.Arch Dermatol. 1972; 105: 869-879Crossref PubMed Scopus (80) Google Scholar, 2Mitsuishi T. Kawana S. Tubular apocrine adenoma of the nose.Eur J Dermatol. 2011; 21: 132PubMed Google Scholar The cells forming the tubular structures show apocrine differentiation with decapitation secretion.1Landry M. Winkelmann R.K. An unusual tubular apocrine adenoma.Arch Dermatol. 1972; 105: 869-879Crossref PubMed Scopus (80) Google Scholar, 2Mitsuishi T. Kawana S. Tubular apocrine adenoma of the nose.Eur J Dermatol. 2011; 21: 132PubMed Google Scholar Although TAA has been histologically well characterized, the dermoscopic features of TAA have not been reported. Here, we present a case of TAA with dermoscopic findings that are indistinguishable from those of basal cell carcinoma (BCC). A 63-year-old man presented with a 2-month history of a small black papule progressively growing on his face. On physical examination, a 3-mm-diameter well-circumscribed black papule with a pearly border was seen on his left cheek (Fig 1, A). Dermoscopic examination revealed telangiectasias and round or oval bluish gray areas that we considered to be short fine telangiectasias (SFTs) and large blue-gray ovoid nests, respectively (Fig 1, B). From the clinical and dermoscopic findings, BCC was initially suspected. Histology showed a number of irregularly shaped tubular structures in the dermis (Fig 2). Telangiectasias were also evident in the upper dermis. The tubular structures contained 2 or more layers of epithelial cells filled with abundant red blood cells (RBCs) and eosinophilic fluid. The luminal layer of the tubular structures was composed of columnar cells, and the outer layer consisted of cuboidal cells. The luminal cells showed active decapitation secretion. Immunohistochemically, positive staining for gross cystic disease fluid protein-15 was observed in the columnar and cuboidal cells and the luminal fluids. The tumor cells showed no significant nuclear atypia or mitotic figures. Neither epidermal invagination nor infiltration of plasma cells was seen. These findings collectively supported a diagnosis of TAA. Clinically, a black lesion with a pearly border developed on our patient's face and showed SFTs and large blue-gray ovoid nests under dermoscopy. Therefore, we initially diagnosed the lesion as BCC. However, subsequent histologic examinations led to a diagnosis of TAA. To our knowledge, to date, no case of TAA showing clinical or dermoscopic resemblance to BCC has been reported. Notably, both SFTs and well-established large blue-gray ovoid nests were observed in the same lesion, although their coexistence is rare in BCC.3Altamura D. Menzies S.W. Argenziano G. Zalaudek I. Soyer H.P. Sera F. et al.Dermoscopy of basal cell carcinoma: morphologic variability of global and local features and accuracy of diagnosis.J Am Acad Dermatol. 2010; 62: 67-75Abstract Full Text Full Text PDF PubMed Scopus (253) Google Scholar Moreover, large blue-gray ovoid nests were arranged in a floriform pattern. The coexistence of SFTs and mature large blue-gray ovoid nests and/or the peculiar arrangement of the ovoid nests might be specific dermoscopic features of TAA. In addition to the typical histologic features of TAA, numerous RBCs in the tubular structures were uniquely observed in this case (Fig 2), presumably giving an atypical color to the lesion. Thus, we speculate that the large blue-gray ovoid nests histologically correspond to the tubular structures filled with numerous RBCs. SFTs also correspond to histologic telangiectasias observed in the upper dermis. In summary, our case suggests that TAA could mimic pigmented BCC clinically and dermoscopically, especially when SFTs and large blue-gray ovoid nests in a floriform pattern are seen dermoscopically.