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21 December 2022 - Case of the Month #522

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Thanks to Drs. Anna Sarah Erem and Gulisa Turashvili, Emory University School of Medicine, Atlanta, Georgia, USA for contributing this case and discussion and to Dr. Jennifer Bennett, University of Chicago, Chicago, Illinois, USA for reviewing the discussion.







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Case of the Month #522

Clinical history:
A 55 year old woman underwent a total hysterectomy with bilateral salpingo-oophorectomy and a sentinel lymph node biopsy for FIGO grade 1 endometrioid adenocarcinoma of the endometrium. One of the lymph nodes showed the following findings.

Histopathology images:


What is your diagnosis?

Click here for diagnosis, test question and discussion:



Diagnosis: Extrapulmonary lymphangioleiomyomatosis

Test question (answer at the end):
Which immunohistochemical stains should be done for confirmation of diagnosis?

A. Desmin, pancytokeratin, cyclin D1, S100
B. Desmin, h-caldesmon, HMB45, MelanA
C. CD10, pancytokeratin, WT1, S100
D. Pancytokeratin, estrogen receptor, WT1, CD10


Stains:

Desmin

HMB45




Discussion:
Lymphangioleiomyomatosis (LAM) belongs to the family of perivascular epithelioid cell neoplasms (PEComas), rare tumors derived from perivascular epithelioid cells with myomelanocytic differentiation. LAM typically involves the lung and presents as a low grade, destructive and progressive disease. However, extrapulmonary LAM may affect the uterus, lymph nodes or other organs (Semin Respir Crit Care Med 2012;33:486). Nodal LAM is often diagnosed in lymph nodes removed for staging purposes in patients with gynecologic neoplasms (Am J Surg Pathol 2015;39:1404).

The morphologic diagnosis of nodal LAM is straightforward in most cases. Typical histologic findings range from a single lesion in the subcapsular sinus to a predominantly extranodal lesion focally involving lymph node parenchyma or a lesion almost entirely replacing a small lymph node. The lesional cells form nests, bundles or fascicles and may have a spindled or epithelioid appearance with grainy, eosinophilic to clear cytoplasm and round to ovoid nuclei with small nucleoli. No cytologic atypia, mitotic activity or necrosis is present (Am J Surg Pathol 2015;39:1404).

Immunohistochemical studies can be helpful in difficult cases and include muscle markers (desmin, h-caldesmon, smooth muscle actin) and melanocytic markers (HMB45, MelanA). Muscle markers usually predominate over the melanocytic markers, although, in an epithelioid predominant morphology, the immunoprofile may be reversed. Of note, HMB45 often exhibits patchy or focal punctate staining. Beta catenin has been shown to have diffuse, strong cytoplasmic, nonnuclear staining pattern, often with accentuated membranous expression sharply demarcating the LAM from surrounding nonneoplastic lymphoid tissue. Overall, HMB45 and beta catenin are more consistently positive markers in nodal LAM (100% of cases) than MelanA (39%) (Am J Surg Pathol 2015;39:1404, Am J Clin Pathol 2011;135:776).

LAM may be associated with tuberous sclerosis complex (TSC), an autosomal dominant genetic disorder characterized by benign neoplasms involving multiple organs due to deleterious mutations in the TSC1 gene encoding hamartin protein or TSC2 gene encoding tuberin protein. Earlier small studies have suggested that the presence of nodal LAM may be a high risk factor for the development of pulmonary LAM, with the size of nodal LAM being the most important predictor (Hum Pathol 2000;31:1242, Chest 1999;115:1041). However, in 2015, the largest study of nodal LAM consisting of 26 patients reported no association with pulmonary LAM, tuberous sclerosis in only 7.7% of the cases and concurrent uterine LAM in 15.4% of the cases (Am J Surg Pathol 2015;39:1015). In another study, all 19 patients lacked association with pulmonary LAM or tuberous sclerosis (Am J Surg Pathol 2015;39:1404). Despite the low likelihood of occurrence, formal evaluation of pulmonary LAM or TSC would still be prudent in patients with incidental nodal LAM.

Test question answer:
B. Desmin, h-caldesmon, HMB45, MelanA

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