9 August 2007 Case of the Week #92
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We recently posted a new chapter on Clinical Chemistry, which contains information on thyroid function tests useful to pathologists and other laboratory personnel. Additional tests will be added over time. A sample entry follows:
Physiology: usual daily production is 50 nmol/day
80% from deiodination of T4 in nonthyroid tissue, 20% arises in thyroid gland from coupling of mono-iodotyrosine plus di-iodotyrosine (i.e. tyrosine plus 3 iodides) and deiodination of T4
This conversion from T4 is blocked by glucocorticoids, amiodarone and propranolol
Metabolized by conjugation with sulfate and conversion to triiodothyroacetic acid (triac)
More T3 is free than T4 (.3% vs. .03%); free T3 is active, protein bound form is inactive and does not enter cells
Values usually parallel T4, but not are usually measured
With nonthyroidal illness (myocardial infarction), T3 levels may be low, although TSH normal
Low T3 syndrome is a strong predictor of death in cardiac patients (Circulation 2003;107:708)
Indications: to diagnose T3 thyrotoxicosis (5% of hyperthyroidism, more common with iodine deficiency), particularly if T4 is normal or mildly elevated
Methodology: competitive immunoassay using enzymes, fluorescence or chemiluminescence
Reference range: serum - 60-160 g/dL (0.9 to 2.5 nmol/L) ??, higher upper limit in pregnancy
May be normal in hyperthyroidism if nonthyroidal illness or taking drugs (amiodarone or propranolol) that reduce T4 to T3 conversion
T3 gives clinicians a sense of the severity and recovery from hyperthyroidism, because it increases more and decreases faster than T4
Note: T3 normal in 15-30% of hypothyroid cases, so not diagnostic; depressed only if severely hypothyroid (T4 < 2 g/dL, 32 nmol/L)
Limitations: difficult to interpret if receiving thyroid preparations containing T3
Conversion factor: convert from ng/dL to nmol/L by multiplying by 0.0154 (conversion chart)
We thank Dr. Juan Jose Segura Fonseca, Hospital San Juan de Dios, San Jose, Costa Rica, for contributing this case and the discussion.This case was reviewed in May 2020 by Dr. Jennifer Bennett, University of Chicago and Dr. Carlos Parra-Herran, University of Toronto.
Case of the Week #92
A 59 yrs old woman complained of abundant vaginal serosanguinous discharge and occasional bleeding during sexual intercourse. On physical examination, a tumor in the vagina was suspected. A small biopsy was diagnosed as a high grade sarcoma NOS. A total hysterectomy was performed. The uterus contained a large, multinodular, solid and polypoid tumor protruding from the cervical canal and attached by a short pedicle (Figure 1), more clearly shown on sagittal section (Figure 2). Microscopically, smooth muscle cells were arranged in interlacing fascicles (Figure 3, Figure 4), with large pleomorphic nuclei (Figure 5, Figure 6). Several mitotic figures were present. Strong immunoreactivity for muscle specific actin (Figure 7) and smooth muscle actin (Figure 8) was present.
What is your diagnosis?
Leiomyosarcoma of the cervix
An estimated 10,520 new malignancies of the uterine cervix were diagnosed in 2004 in the United States (CA Cancer J Clin 2004;54:8). Pure cervical sarcomas are rare. Young estimated that sarcomas constituted 0.55% of cervical malignancies in the U.S. during 1973 to 1977 (National Cancer Institute SEER: Incidence and mortality data: 1973-1977. Monograph 57, Bethesda, MD: NIH-NCI-81-2330:1981), and Wright identified only 8 pure sarcomas in 1583 cervical malignancies (0.5%) during 1986 to 2003 (Gynecol Oncol 2005;99:348).
As a primary cervical tumor, leiomyosarcoma is very rare, particularly if cases with possible origin in the lower uterine segment are excluded. However, definitive cases have been reported after subtotal or supracervical hysterectomy for other reasons (Ginekol Pol 2002;73:613). Fadare found only 30 reported cases of primary cervical leiomyosarcoma after literature review (Diagn Pathol 2006;18:30). They occur in peri- and postmenopausal women ages 40 to 60 years, and most commonly present with abnormal vaginal bleeding, abdominopelvic pain and a palpable cervical mass.
Grossly, cervical leiomyosarcomas are typically large, up to 12 cm, and either protrude from the cervical canal as large polypoid tumors or thicken and expand it circumferentially. Microscopically they display typical features of classic leiomyosarcoma, but may also be epithelioid (Gynecol Oncol 2005;97:957), myxoid or xanthomatous (Int J Gynecol Pathol 1998;17:89).
The differential diagnosis depends on the features present, and may include melanoma, metastatic carcinoma, epithelioid sarcoma or myxoid tumors.
Prognosis is poor, often with death due to distant metastases (Cancer 1973;31:1176).
Nat Pernick, M.D., President
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