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Diagnostics Histology, Training and education

Case of the Month

A 61-year-old female with systemic lupus erythematosus, on mycophenolate mofetil, presented with a three-week fever, hypoxia, and hypotension. Images show findings in bone marrow biopsy and peripheral blood smear.

What is the most likely diagnosis?

a. Systemic infection by Talaromyces marneffei
b. Disseminated histoplasmosis
c. Invasive candidiasis
d. Visceral leishmaniasis
e. Toxoplasmosis

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We will reveal the answer next month.

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The Case of the Month series is curated by Anamarija M. Perry, University of Michigan.

B. Basal cell adenoma

Basal cell adenomas typically present as well-circumscribed nodules that are often encapsulated. On smear preparations, the neoplastic population is composed of basaloid cells characterized by round to ovoid nuclei, smooth nuclear contours, granular chromatin distribution, and scant amounts of cytoplasm arranged in nests and trabeculae, sometimes with vague peripheral palisading of cells in cell clusters. The amount of matrix can be variable and can include peripheral bands of hyaline matrix around cell aggregates as well as smooth-countered hyaline globules. In membranous types of basal cell adenoma, the basaloid cells are characteristically arranged in trabeculae that are distinctly outlined by a ribbon of dense hyaline matrix material. Without the characteristic morphologic findings of the membranous type, it would be difficult to differentiate basal cell adenoma from other basaloid salivary gland neoplasms, such as adenoid cystic carcinoma, cellular pleomorphic adenoma, or other metastatic basaloid tumors (i.e., basaloid squamous cell carcinoma and basal cell carcinoma). Additionally, morphologic differentiation of basal cell adenoma from its malignant counterpart, basal cell adenocarcinoma, would be impossible, because the key difference is identification of an infiltrative growth pattern in basal cell adenocarcinoma.

On surgical resection specimens, these tumors often show a mixture of architectural patterns, such as solid, trabecular, tubular, and membranous patterns composed of basaloid cells with variable peripheral palisading myoepithelial cells. Immunohistochemistry for cytokeratin cocktail highlights all tumor cells, but is most notable in ductal cells, whereas the myoepithelial cells are highlighted by calponin, p63, and smooth muscle actin. Although some studies have reported alterations at chromosomes 8, 19, and 16 – or, rarely, translocations and inversions – in basal cell adenomas, no characteristic genetic alteration has been found to be diagnostic of a basal cell adenoma (1)(2)(3). Basal cell adenomas can occur in association with Brook-Spiegler syndrome, an autosomal dominant disorder due to mutations of the CYCLD gene.

These tumors generally have a good prognosis with a low recurrence rate. However, it is important to note that the membranous type has a higher recurrence rate of approximately 25 percent (4).

Submitted by Madelyn Lew, Associate Professor in the Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA.

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  1. HR Choi et al., “Molecular analysis of chromosome 16q regions in dermal analogue tumors of salivary glands: a genetic link to dermal cylindroma?”, Am J Surg Pathol, 26, 778 (2002). PMID: 12023583.
  2. AK el-Naggar et al., “Genotypic alterations in benign and malignant salivary gland tumors: histogenetic and clinical implications”, Am J Surg Pathol, 21:, 91 (1997). PMID: 9199647.
  3. H Sjogren et al., “Observations by G-banding and multicolor spectral karyotyping in a salivary gland basal cell adenoma”, Virchows Arch, 442, 86 (2003). PMID: 12596771.
  4. JG Batsakis et al., “Basaloid monomorphic adenomas”, Ann Otol Rhinol Laryngol, 100, 687 (1991). PMID: 18722522.
     

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