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INDIANA ASSOCIATION OF PATHOLOGISTS


November 2019

A 36-year-old 12-week pregnant Caucasian woman with changing mole on her right medial thigh

Contributors: 



Mohamed Amin Mustafa, MBBS

Resident Education Chief-PGY4 

Department of Clinical Pathology & Laboratory Medicine

Indiana University School of Medicine




Ahmed Alomari, MD

Assistant Professor of Clinical Pathology & Laboratory Medicine

Indiana University School of Medicine


Clinical history:  We present a 36-year-old 12-week pregnant Caucasian woman with a changing mole on her right medial thigh. An Initial biopsy showed a polypoid compound melanocytic proliferation with central “sheet-like” growth pattern. Up to 5 mitoses/mm2 were counted, including few deep mitoses. HMB-45 showed prominent stratification and p16 was mosaic. This was read as nevoid melanoma with 1.38 mm Breslow depth. The patient underwent excision with sentinel lymph node biopsy which showed few superficial nodal deposits of HMB-45-weakly positive melanocytes. This was interpreted as positive for metastatic melanoma and she was transferred to our institution for further management.

Gross Examination: An 8.0 x 3.3 cm elliptical skin excised to a depth of 2.0 cm with a 1.9 cm blue-dyed sentinel lymph node (greatest dimension).

Microscopic examination and immunohistochemistry: Upon review, the lesion was noted to be relatively small with prominent cytological and architectural maturation. No atypical mitoses were identified and comparative genomic hybridization revealed no chromosomal gains or losses. The nodal deposits were cytologically bland with no mitotic activity and only weak HMB-45 reactivity.

For PC users, right click to open image in a new window, then zoom to enlarge.

Figure1 A: Low power view  of compound melanocytic nevus with sheet-like growth pattern.

                                

Fig. 1A

Figure 1B:High power view (B) of compound melanocytic nevus with sheet-like growth pattern.


   Fig. 1B

Figure 1C: The nevus is positive for HMB45


 Fig.1C

Figure 1D: The nevus is positive for SOX10.


Fig. 1D

Figure 1E: Mosaic p16 pattern


Fig. 1F Bland nodal nevi; by SOX10 


Fig. 1F

Fig. 1G HMB45


Fig. 1G

Fig.1H HMB45


Fig. 1H

November 2019 Final Diagnosis and Discussion


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