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Pathology International 2014; 64: 585–587
doi:10.1111/pin.12210
Letter to the Editor Unexpected finding in a femoral head specimen after elective total hip arthroplasty To the Editor: Mastocytosis is a myeloproliferative neoplasm with cutaneous and/or systemic manifestations. The disease occurs in all age groups, with the cutaneous version more common in children and systemic mastocytosis (SM) generally occurring later in life. The initial presentation of SM ranges from no or mild nonspecific constitutional symptoms to end organ dysfunction or pain associated with the site(s) of disease. We describe a case of unexpected systemic mastocytosis diagnosed on routine pathology evaluation of a femoral head from a total hip arthroplasty (THA) procedure. Our experience highlights the importance of vigilance when evaluating apparently routine specimens submitted for suspected bone and joint pathology. A 49 year-old otherwise healthy woman presented with bilateral hip pain, worse on the right than on the left side. A magnetic resonance imaging scan showed multifocal cartilage loss on both sides of the right hip joint and tears of the anterior and superior labrum. The pain only partially improved with conservative measures and eventually caused severe limitation in her normal daily activities. Later imaging studies showed dysplasia and small osteophytes on both femoral head surfaces. Intra-articular corticosteroid injections provided short-term relief, and she ultimately opted for bilateral THA performed as sequential procedures. A pre-operative complete blood count was unremarkable, with normal absolute values for all white blood cell lineages. The femoral heads were submitted to surgical pathology and showed mild osteoarthritis grossly. Histologic review confirmed mild osteoarthritis but also showed an abnormal bone marrow leading to subspecialty consultation with hematopathology and further diagnostic evaluation. Grossly the right femoral head showed eburnation, osteophytes and subchondral sclerosis on the cut surface, consistent with osteoarthritis. Microscopically, the bone marrow was hypercellular and showed polyclonal B- and T- cell lymphoid aggregates with admixed eosinophils and histiocytes. Large collections of atypical mast cells with spindled and round morphology (Fig. 1a and insert) were closely associated to the lymphohistiocytic aggregates. In addition, atypical, faintly granular, mast cells were dispersed singly in an interstitial pattern throughout the marrow space. Immunohistochemistry was performed on formalin-fixed paraffin embedded tissue using the Leica BOND system (New-
Disclosure: The authors have no relevant disclosures.
castle, UK) with antibodies directed against the following antigens: CD1a, CD2, CD3, CD15, CD20, CD30, CD117 (C-KIT), PAX-5 (Leica, premade antibodies diluted by the manufacturer), mast cell tryptase (1:200, Dako, Carpinteria, CA, USA), CD45 (premade antibodies diluted by the manufacturer, Biogenex, Freemont, CA, USA). Standard immunohistochemical protocols were followed with negative and positive controls run concurrently. The abnormal mast cells expressed CD117 (C-KIT), tryptase and CD25 (Fig. 1b–d) but lacked CD2 and CD30 (not shown). Additionally, the atypical cells were negative for CD20, CD3, CD15, PAX-5 and CD1a. Stains for acid-fast bacilli and fungi were negative. The surgical specimen from the subsequent left THA showed similar histologic features, consistent with a mast cell neoplasm. Follow up laboratory testing performed later on the peripheral blood revealed an elevated serum tryptase level (26.8 ng/mL; normal
Pathology International 2014; 64: 585–587
doi:10.1111/pin.12210
Letter to the Editor Unexpected finding in a femoral head specimen after elective total hip arthroplasty To the Editor: Mastocytosis is a myeloproliferative neoplasm with cutaneous and/or systemic manifestations. The disease occurs in all age groups, with the cutaneous version more common in children and systemic mastocytosis (SM) generally occurring later in life. The initial presentation of SM ranges from no or mild nonspecific constitutional symptoms to end organ dysfunction or pain associated with the site(s) of disease. We describe a case of unexpected systemic mastocytosis diagnosed on routine pathology evaluation of a femoral head from a total hip arthroplasty (THA) procedure. Our experience highlights the importance of vigilance when evaluating apparently routine specimens submitted for suspected bone and joint pathology. A 49 year-old otherwise healthy woman presented with bilateral hip pain, worse on the right than on the left side. A magnetic resonance imaging scan showed multifocal cartilage loss on both sides of the right hip joint and tears of the anterior and superior labrum. The pain only partially improved with conservative measures and eventually caused severe limitation in her normal daily activities. Later imaging studies showed dysplasia and small osteophytes on both femoral head surfaces. Intra-articular corticosteroid injections provided short-term relief, and she ultimately opted for bilateral THA performed as sequential procedures. A pre-operative complete blood count was unremarkable, with normal absolute values for all white blood cell lineages. The femoral heads were submitted to surgical pathology and showed mild osteoarthritis grossly. Histologic review confirmed mild osteoarthritis but also showed an abnormal bone marrow leading to subspecialty consultation with hematopathology and further diagnostic evaluation. Grossly the right femoral head showed eburnation, osteophytes and subchondral sclerosis on the cut surface, consistent with osteoarthritis. Microscopically, the bone marrow was hypercellular and showed polyclonal B- and T- cell lymphoid aggregates with admixed eosinophils and histiocytes. Large collections of atypical mast cells with spindled and round morphology (Fig. 1a and insert) were closely associated to the lymphohistiocytic aggregates. In addition, atypical, faintly granular, mast cells were dispersed singly in an interstitial pattern throughout the marrow space. Immunohistochemistry was performed on formalin-fixed paraffin embedded tissue using the Leica BOND system (New-
Disclosure: The authors have no relevant disclosures.
castle, UK) with antibodies directed against the following antigens: CD1a, CD2, CD3, CD15, CD20, CD30, CD117 (C-KIT), PAX-5 (Leica, premade antibodies diluted by the manufacturer), mast cell tryptase (1:200, Dako, Carpinteria, CA, USA), CD45 (premade antibodies diluted by the manufacturer, Biogenex, Freemont, CA, USA). Standard immunohistochemical protocols were followed with negative and positive controls run concurrently. The abnormal mast cells expressed CD117 (C-KIT), tryptase and CD25 (Fig. 1b–d) but lacked CD2 and CD30 (not shown). Additionally, the atypical cells were negative for CD20, CD3, CD15, PAX-5 and CD1a. Stains for acid-fast bacilli and fungi were negative. The surgical specimen from the subsequent left THA showed similar histologic features, consistent with a mast cell neoplasm. Follow up laboratory testing performed later on the peripheral blood revealed an elevated serum tryptase level (26.8 ng/mL; normal
