Kikuchi's disease (KD) is an idiopathic, self-limited necrotizing lymphadenitis that can clinically and histologically mimic high-grade lymphoma, including Hodgkin's disease, or can be mistaken for the lymphadenitis of systemic lupus erythematosus (SLE). Involvement of extranodal sites is unusual but well documented, especially in Asia, where KD is more common than in North America or Europe. The successful distinction of KD from malignant lymphoma and SLE is imperative for the appropriate treatment of affected patients. We describe five patients with cutaneous involvement by KD, all of whom presented with fever, lymphadenopathy, and an eruption on the skin of the upper body, which in one case was clinically suspected to be due to SLE and in another, polymorphous light eruption. The patients ranged in age from 10 months to 42 years (median, 33 years) and included three females and two males. All five patients had negative serologic studies for collagen vascular disease. Each patient had a lymph node biopsy showing the typical necrotizing lymphadenitis of KD. Skin biopsies from all five patients shared a specific constellation of histologic features: vacuolar interface change with necrotic keratinocytes, a dense lymphohistiocytic superficial and deep perivascular and interstitial infiltrate, varying amounts of papillary dermal edema, and abundant karyorrhectic debris with a conspicuous absence of neutrophils and a paucity of plasma cells, paralleling the nodal histology in KD. CD68 immunohistochemistry on paraffin-embedded sections showed many histiocytes and plasmacytoid monocytes in all cases, whereas CD3, CD4, and CD8 showed highly variable staining among the cases. There was only rare staining with TIA-1 and CD30. We believe that the papular eruption of KD has recognizable histopathologic features and that a CD68 stain that marks many cells that initially seem to be lymphocytes can be performed to confirm the diagnosis.

Heavily pigmented melanocytic neoplasms are genotypically and phenotypically diverse. Recently, a subset of this histopathologic spectrum was shown to harbor recurrent genetic alterations in the gene-encoding protein kinase A regulatory subunit-α (PRKAR1A). To date, no histopathologic descriptions of melanomas arising from this pathway have been described. We present a case of a darkly pigmented papule arising on the posterior neck of a 28-year-old man. Microscopically, the heavily pigmented compound melanocytic proliferation was centered in the dermis with permeation into the superficial subcutis. Tumor cells were arranged in large confluent nests and fascicles and lacked maturation with descent. The epithelioid melanocytes were characterized by enlarged vesicular nuclei with prominent nucleoli, nuclear pleomorphism, and plentiful gray-brown granular cytoplasm. Mitotic figures were readily identified. By immunohistochemistry, melanocytes were positive for mutant BRAF V600E and showed loss of Prkar1α and p16 expression. A multiplex MART-1/tyrosinase/phosophohistone-H3 immunostain demonstrated an increased mitotic index in melanocytes. The combination of highly atypical cytomorphology and architecture, increased mitoses, and p16 expression loss compelled the diagnosis of melanoma. Overall, we present the first clinicopathologic description of a PRKAR1A-inactivated melanoma to highlight morphological features and discuss mimics that may enter the differential diagnosis.

Amphetamine and methamphetamine are commonly abused central nervous system stimulants. We describe a rapid new derivatization of amphetamine and methamphetamine using 2,2,2-trichloroethyl chloroformate for gas chromatography-mass spectrometric analysis. Amphetamine and methamphetamine, along with N-propyl amphetamine (internal standard), were extracted from urine using 1-chlorobutane. The derivatization with 2,2,2-trichloroethyl chloroformate can be achieved at room temperature in 10 minutes. The electron ionization mass spectrum of amphetamine 2,2,2-trichloroethyl carbamate showed two weak molecular ions at tnlz 309 and 311, but showed diagnostic strong peaks at mlz 218, 220, and 222. In contrast, chemical ionization of the mass spectrum of amphetamine 2,2,2-trichloroethyl carbamate showed strong (M + 1) ions at tnlz 310 and 312 and other strong diagnostic peaks at tnlz 274 and 276. The major advantages of this derivative are the presence of a diagnostic cluster of peaks due to the isotopic effect of three chlorine atoms (isotopes 35 and 37) in the derivatized molecule and the relative ease of its preparation. We also observed strong molecular ions for derivatized methamphetamine in the chemical ionization mass spectrum, but the molecular ions were Amphetamine and methamphetamine are central nervous system stimulants that produce alertness, wakefulness, increased energy, and reduced hunger.1 -2 Amphetamine and methamphetamine are commonly abused and have resulted in many deaths from overdoses. 3 In Sweden, amphetamine is the most commonly abused drug. 4 Because of widespread abuse of amphetamine and methamphetamine, drug testing for very weak in the electron ionization mass spectrum. We used the scan mode of mass spectrometry in all analyses. When using a urine standard containing 1,000 ng/mL of amphetamine (a 7.4-nmol/L concentration) and methamphetamine (a 6.7-|imol/L concentration), the withinrun precisions were 4.8% for a m p h e t a m i n e and 3.6% for methamphetamine. The corresponding between-run precisions were 5.3% for amphetamine and 6.7% for methamphetamine. The assay was linear for amphetamine and methamphetamine concentrations of 250 to 5,000 ng/mL (amphetamine, 1.9-37.0 nmol/L; methamphetamine, 1.7-33.6 nmol/L). The detection limit was 100 ng/mL (amphetamine, 0.74 (imol/L; methamphetamine, 0.67 |imol/L) using the scan mode of electron ionization mass spectrometry. We observed good a correlation between the concentrations of amphetamine and methamphetamine in five urine specimens positive for amphetamines using the more conventional pentafluoropropionyl derivative and our new derivative using 2,2,2-trichloroethyl chloroformate.

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