The images for this month’s challenge were submitted by Andrew R. Hsu, MD, and Walter W. Virkus, MD, who provided the following information:

A 16-year old African-American male high school football player was seen by his primary care provider 5 days after sustaining a contact injury to the anterior portion of his right shoulder during practice. The patient had pain and weakness with overhead activities and range of motion testing. He had no numbness, tingling, or any radiation of pain.

Plain radiographs showed an enlarged, cystic-appearing glenoid with a sclerotic rim (Fig. 1A). MRI showed an abnormal multilobulated, destructive lesion of the right glenoid with isointense signal to muscle on T1-weighted images (Fig. 1B). The patient underwent a CT-guided biopsy (Fig. 1C) of the lesion, resulting in a diagnosis of osteomyelitis, despite normal inflammatory lab values (white blood cell count, C-reactive protein, erythrocyte sedimentation rate), a negative gram stain, and negative biopsy cultures. At that point the patient was referred to the orthopaedic oncology clinic and scheduled for a one-stage open biopsy with the authors to evaluate intraoperative frozen section pathology and cultures.

A posterior approach was used and a reddish-purplish material was found in the medullary cavity of the glenoid. The material was curetted and sent for frozen section pathology and cultures. The initial pathology diagnosis was Langerhans cell histiocytoma (LCH), so the cystic lesion was fully curetted and packed with cancellous allograft. The patient was discharged the following day in a right long-arm post-mold splint with non–weight-bearing restriction.

A second pathology opinion several days later, however, found histiocytes with lymphocytic nuclei in the cytoplasm (Fig. 1D) and immunohistochemical staining that was CD68 (PGM1) positive, CD4 positive, S-100 positive, CD30 negative, and CD1a negative, thus excluding the diagnosis of LCH. What’s your diagnosis?

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Find the answer to this month’s challenge below

Answer
This month’s challenge appears on page 15. According to Drs. Hsu and Virkus, the final diagnosis was determined to be Rosai-Dorfman disease. At 2-week follow-up, the patient had a significant decrease in pain and good passive range of motion (ROM) with pain only at extremes. He received physical therapy and ROM continued to increase, with radiographs showing good consolidation of the lesion. At 6-month follow-up, the patient was able to return to activities without disease recurrence or pain.

(Photos on above links are reprinted with permission from: Hsu AR, Bhatia S, Kang RW, Arvanitis L, Nicholson GP, Virkus WW. Extranodal Rosai-Dorfman disease presenting as an isolated glenoid lesion in a high school athlete. J Shoulder Elbow Surg. 2012 Jan;21(1):e6-e11. Epub 2011 Aug 26.)