Lobular breast carcinoma metastasis to skeletal muscle, two case reports diagnosed by ultrasound guided FNA with evaluation of the roles of interventional cytopathology.

Skeletal muscle metastasis from breast carcinoma is a relatively rare clinical entity. We report two cases of breast cancer metastatic to the skeletal muscle, diagnosed by ultrasound guided fine needle aspiration (US-FNA) biopsy done by interventional cytopathologists at an outpatient cytopathology center. Our two patients presented with lower anterior neck firmness and chest wall mass, respectively. Ultrasound evaluation of our first case demonstrated hypo-echoic thickened anterior strap muscles while in the second case there was significant distortion of the anatomy from previous surgeries. It was necessary to proceed with FNA biopsy even when their ultrasound findings were equivocal, to establish a definite rapid diagnosis. The immediate onsite evaluation findings were suggestive of malignancy in both cases with subsequent core biopsy confirming the diagnosis of metastatic breast carcinoma. In cytopathology, point-of-care (POC) ultrasound is used as an adjunct tool that offers visual guidance during FNA of nonpalpable masses and enables sampling of lesional "hot" spots to ensure specimen adequacy. Studies have demonstrated a reduction in FNA nondiagnostic rates with the use of ultrasound-guidance consequently reducing health care costs associated with nondiagnostic FNAs. US-FNA also provides adequate samples for cell block preparations. Metastatic lobular carcinoma of the breast has a wide range of clinical presentations and a high level of suspicion is advised. Cytopathologists-performed US-FNA is a proven, less-invasive, cost-effective tool that provides timely cytologic diagnosis.

Fluids--good and bad actors: observations from the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytology.

CONTEXT: Body cavity fluid examination presents a common and sometimes difficult diagnostic challenge in daily cytology practice. Separating benign from malignant cellular changes may require meticulous screening, careful scrutiny of cellular features, and an understanding of the range of reactive changes. We use the data from the College of American Pathologists (CAP) Interlaboratory Comparison Program in Nongynecologic Cytology (NGC) to identify characteristics of fluids that place them at opposite ends of the diagnostic spectrum. OBJECTIVE: To assess the features of individual body cavity fluid slides that demonstrated good performance characteristics and compare them to slides that were poor performers. DESIGN: A databank of 10 396 laboratory responses, including a variety of malignant and benign cases obtained from 1997 through 2001, was used to select cases. A cumulative slide history was used to identify slides that performed well or poorly in each reference diagnosis. Cases were confirmed by consensus of 4 CAP Cytopathology Resource Committee members. Observations and characterizations of good and bad performers in each category were recorded and summarized. RESULTS: Percentage of concordance of poor performers ranged from 0% to 58%. Conversely, good performers were identified with high concordance of laboratory diagnosis in each reference category (>80%). Several patterns emerged. Poorly performing cases of adenocarcinoma consisted of slides with rare tumor cells, hypercellular malignant cases without 2 cell populations, and cases with single cells. Poor performance in confirmed squamous cell carcinoma cases related to rare cells without keratinization. Small cell carcinoma and melanoma cases performed poorly when there were few malignant cells. Lymphoma cases demonstrated poor performance when there were abundant pleomorphic lymphoid cells or when rare Reed- Sternberg-like cells were present. Reactive or negative slides performed best with a polymorphous population; poor performers were those with a predominant lymphocyte population mistaken for a hematopoietic neoplasm. CONCLUSION: Close attention to classic cytologic criteria and careful examination of slides may enhance the educational experience of participants and the performance characteristics of body cavity fluid specimens in the CAP NGC program. Lessons from bad actors in the CAP NGC program may increase awareness of potential diagnostic problems in daily practice or help identify areas for laboratory quality improvement.