Spindle cells seen in fine‐needle aspiration biopsy (FNAB) of the mediastinal lesions can be a component of a wide variety of benign and malignant conditions. Few of these conditions, however, are described in the FNA cytopathology literature. This review discusses the cytopathologic features, differential diagnoses, and potential pitfalls of a variety of lesions with a significant component of spindle cells encountered in mediastinal FNAB. The cytopathology files from four institutions were searched for cases of mediastinal FNAB containing a spindle‐cell component that was a key or predominant cytologic feature of the diagnostic specimen. The cytomorphologic features of these cases were analyzed, and their differential features are discussed. Of 196 mediastinal FNABs, 22 (11%) were lesions with significant spindle‐cell component: granulomatous inflammation (four); benign nerve sheath tumor (four); thymic cyst (two); spindle‐cell thymoma (two); large‐cell non‐Hodgkin's lymphoma with sclerosis (two); nodular sclerosing Hodgkin's disease (two); liposarcoma (two); spindle‐cell squamous carcinoma possibly arising in a teratoma (one); unspecified high‐grade sarcoma (one); spindle‐cell malignant melanoma (one); and nonspecific fibrous tissue (one). The cytologic features of each lesion were analyzed as an aid for accurate classification. These findings were correlated with radiologic and clinical information when available. The value of ancillary studies performed on aspirated material in selected cases was also reviewed. FNA of mediastinal lesions with significant spindle‐cell morphology represents an infrequent and heterogeneous group of entities that may pose significant diagnostic challenges. This review presents the salient cytopathologic features of various spindle‐cell lesions of the mediastinum with particular emphasis on differential diagnosis and pitfalls. The pathologist must use caution when interpreting these lesions and ancillary studies may be of significant value in selected cases. Diagn. Cytopathol. 1997;17:167–176. © 1997 Wiley‐Liss, Inc.

To the Editor: A 48-year-old woman being treated with lenalidomide for kappa light chain multiple myeloma presented with severe rash associated with urticaria, pruritus, and fever. The patient was initially diagnosed with Stage II breast cancer (ER/PR+ and HER-2neu negative) in 2003 and underwent treatment with lumpectomy followed by four cycles of Adriamycin and Cyclophosphamide followed by two cycles of Paclitaxel and then switched to an additional two cycles of Taxotere because of poor tolerance. This was followed by radiation therapy and hormonal therapy. Two years later she was diagnosed with multiple myeloma. As a result of her negative prior experience with chemotherapy and steroids she refused treatment with either and was therefore initially treated with single agent thalidomide. Thalidomide treatment had to be discontinued due to a similar reaction manifesting with severe rash, urticaria, and pruritus, which was thought to be a Type I (IgE mediated) hypersensitivity reaction. When lowered to 50 mg the patient continued to experience side effects necessitating its permanent discontinuation. She was subsequently treated with bortezomib which had to be discontinued secondary to increasing neuropathy. Lenalidomide treatment at the standard dose of 25 mg resulted in the reaction described above which was similar to the reaction she developed on thalidomide, which is not surprising given the structural similarities between the two drugs. The patient was subsequently referred to Allergy-Immunology for desensitization in August 2006. The patient was desensitized using the protocol shown in Table I. In brief, lenalidomide was dissolved in normal saline and diluted to concentrations of 0.025, 0.25, and 2.50 mg/ml. She was given gradually increasing strengths to take orally at 15-to 20-min interval. During the desensitization she had her blood pressure, heart rate, temperature, pulse oximetry, and peak flow monitored. She tolerated the escalating doses with no reaction and was subsequently begun on lenalidomide 15 mg daily, and continues to tolerate daily continuous dosing with no evidence of recurrent hypersensitivity. The patient remains asymptomatic in a PR as defined by the International Working Group Uniform Response Criteria, and also remains free from any evidence of recurrent breast cancer. This represents the first case of successful desensitization to lenalidomide that we are aware of. Since this drug has become an integral component of multiple myeloma therapy this represents an important option for patients who otherwise would not be able to tolerate lenalidomide.

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A 37-year-old man with hairy cell leukemia was found incidentally to have a right inguinal hernia. Microscopic examination of the resected herniorrhaphy specimen disclosed dense transmural infiltration by hairy cells. Electron-microscopic and immunoperoxidase studies confirmed the presence of surface cytoplasmic projections and B cell phenotype, respectively, of the infiltrating cells. This case is, to our knowledge, the first reported instance of hairy cell leukemia involving a hernial sac and demonstrates the capacity of hairy cells to infiltrate unexpected soft-tissue sites.